Chessboard calibration

// typedefs

typedef std::map<std::string, TImageCalibData> mrpt::vision::TCalibrationImageList;
typedef void(*)(const TImageStereoCallbackData&d, void*user_data) mrpt::vision::TSteroCalibCallbackFunctor;
typedef std::vector<TImageStereoCalibData> mrpt::vision::TCalibrationStereoImageList;

// structs

struct mrpt::vision::TImageCalibData;
struct mrpt::vision::TImageStereoCalibData;
struct mrpt::vision::TImageStereoCallbackData;
struct mrpt::vision::TStereoCalibParams;
struct mrpt::vision::TStereoCalibResults;

// global functions

bool mrpt::vision::checkerBoardCameraCalibration(
    TCalibrationImageList& images,
    unsigned int check_size_x,
    unsigned int check_size_y,
    double check_squares_length_X_meters,
    double check_squares_length_Y_meters,
    mrpt::img::TCamera& out_camera_params,
    bool normalize_image = true,
    double* out_MSE = nullptr,
    bool skipDrawDetectedImgs = false
    );

bool mrpt::vision::checkerBoardCameraCalibration(
    TCalibrationImageList& images,
    unsigned int check_size_x,
    unsigned int check_size_y,
    double check_squares_length_X_meters,
    double check_squares_length_Y_meters,
    mrpt::math::CMatrixDouble33& intrinsicParams,
    std::vector<double>& distortionParams,
    bool normalize_image = true,
    double* out_MSE = nullptr,
    bool skipDrawDetectedImgs = false
    );

bool mrpt::vision::findChessboardCorners(
    const mrpt::img::CImage& img,
    std::vector<mrpt::img::TPixelCoordf>& cornerCoords,
    unsigned int check_size_x,
    unsigned int check_size_y,
    bool normalize_image = true
    );

bool mrpt::vision::checkerBoardStereoCalibration(TCalibrationStereoImageList& images, const TStereoCalibParams& params, TStereoCalibResults& out_results);

Typedefs

typedef std::map<std::string, TImageCalibData> mrpt::vision::TCalibrationImageList

A list of images, used in checkerBoardCameraCalibration.

See also:

checkerBoardCameraCalibration

typedef void(*)(const TImageStereoCallbackData&d, void*user_data) mrpt::vision::TSteroCalibCallbackFunctor

Prototype of optional user callback function.

typedef std::vector<TImageStereoCalibData> mrpt::vision::TCalibrationStereoImageList

A list of images, used in checkerBoardStereoCalibration.

See also:

checkerBoardStereoCalibration

Global Functions

bool mrpt::vision::checkerBoardCameraCalibration(
    TCalibrationImageList& images,
    unsigned int check_size_x,
    unsigned int check_size_y,
    double check_squares_length_X_meters,
    double check_squares_length_Y_meters,
    mrpt::img::TCamera& out_camera_params,
    bool normalize_image = true,
    double* out_MSE = nullptr,
    bool skipDrawDetectedImgs = false
    )

Performs a camera calibration (computation of projection and distortion parameters) from a sequence of captured images of a checkerboard.

Parameters:

input_images	[IN/OUT] At input, this list must have one entry for each image to process. At output the original, detected checkboard and rectified images can be found here. See TImageCalibData.
check_size_x	[IN] The number of squares in the checkerboard in the X direction.
check_size_y	[IN] The number of squares in the checkerboard in the Y direction.
check_squares_length_X_meters	[IN] The size of each square in the checkerboard, in meters, in the X axis.
check_squares_length_Y_meters	[IN] This will typically be equal to check_squares_length_X_meters.
intrinsicParams	[OUT] The 3x3 intrinsic parameters matrix. See https://www.mrpt.org/Camera_Parameters
distortionParams	[OUT] The 1x4 vector of distortion parameters: k1 k2 p1 p2. See https://www.mrpt.org/Camera_Parameters
normalize_image	[IN] Select OpenCV flag
out_MSE	[OUT] If set to !=nullptr, the mean square error of the reprojection will be stored here (in pixel units).
skipDrawDetectedImgs	[IN] Whether to skip the generation of the undistorted and detected images in each TImageCalibData

Returns:

false on any error (more info will be dumped to cout), or true on success.

See also:

The camera-calib-gui application is a user-friendly GUI to this class.

CImage::findChessboardCorners, checkerBoardStereoCalibration

bool mrpt::vision::findChessboardCorners(
    const mrpt::img::CImage& img,
    std::vector<mrpt::img::TPixelCoordf>& cornerCoords,
    unsigned int check_size_x,
    unsigned int check_size_y,
    bool normalize_image = true
    )

Look for the corners of a chessboard in the image using one of two different methods.

Look for the corners of a chessboard in the image.

The search algorithm will be OpenCV’s function cvFindChessboardCorners or its improved version published by M. Rufli, D. Scaramuzza, and R. Siegwart. See: http://robotics.ethz.ch/~scaramuzza/Davide_Scaramuzza_files/Research/OcamCalib_Tutorial.htm and the papers:

1. Scaramuzza, D., Martinelli, A. and Siegwart, R. (2006), A Toolbox for Easily Calibrating Omnidirectional Cameras, Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2006), Beijing, China, October 2006.
1. Scaramuzza, D., Martinelli, A. and Siegwart, R., (2006). “A Flexible Technique for Accurate Omnidirectional Camera Calibration and Structure from Motion”, Proceedings of IEEE International Conference of Vision Systems (ICVS’06), New York, January 5-7, 2006.
1. Rufli, M., Scaramuzza, D., and Siegwart, R. (2008), Automatic Detection of Checkerboards on Blurred and Distorted Images, Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2008), Nice, France, September 2008.

After detecting the corners with either method, it’s called “cvFindCornerSubPix” to achieve subpixel accuracy.

Parameters:

cornerCoords	[OUT] The pixel coordinates of all the corners.
check_size_x	[IN] The number of squares, in the X direction
check_size_y	[IN] The number of squares, in the Y direction
normalize_image	[IN] Whether to normalize the image before detection
cornerCoords	[OUT] The pixel coordinates of all the corners.
check_size_x	[IN] The number of squares, in the X direction
check_size_y	[IN] The number of squares, in the Y direction
normalize_image	[IN] Whether to normalize the image before detection
useScaramuzzaMethod	[IN] Whether to use the alternative, more robust method by M. Rufli, D. Scaramuzza, and R. Siegwart.

Returns:

true on success

See also:

mrpt::vision::checkerBoardCameraCalibration, drawChessboardCorners

bool mrpt::vision::checkerBoardStereoCalibration(
    TCalibrationStereoImageList& images,
    const TStereoCalibParams& params,
    TStereoCalibResults& out_results
    )

Optimize the calibration parameters of a stereo camera or a RGB+D (Kinect) camera.

This computes the projection and distortion parameters of each camera, and their relative spatial pose, from a sequence of pairs of captured images of a checkerboard. A custom implementation of an optimizer (Levenberg-Marquartd) seeks for the set of selected parameters to estimate that minimize the reprojection errors.

See also the ready-to-use application: kinect-calibrate

Parameters:

input_images	[IN/OUT] At input, this list must have one entry for each image to process. At output the original, detected checkboard and rectified images can be found here. See TImageCalibData.
params	[IN] Mandatory: the user must provide the size of the checkerboard, which parameters to optimize and which to leave fixed to zero, etc.
out_results	[OUT] The results of the calibration, and its uncertainty measure, will be found here upon return.

Returns:

false on any error (more info will be dumped to cout), or true on success.

See also:

CImage::findChessboardCorners, checkerBoardCameraCalibration, mrpt::hwdrivers::CKinect